Search systems having an ambiguous search function that when searching a document produce as hits parts that do not perfectly match the search keyword are known. For example, Patent Literature 1 (Unexamined Japanese Patent Application Kokai Publication No. H8-235212) discloses technology for executing an ambiguous search using a search index that records the position of characters appearing in the text being searched. With the technology of Patent Literature 1, first the positions at which characters appearing in the search keyword appear in the text being searched are acquired. Then, the degree of similarity is added when these characters appear in character strings being searched due to errors within a prescribed range from appearance position in the keywords. Ambiguous searches are conducted based on this calculated degree of similarity.
With the art disclosed in Patent Literature 1, the same degree of similarity is calculated for search target character strings having the same number of characters appearing in the search target with errors within a prescribed range from positions where the keywords appear. Consequently, character strings of the search target that are extremely close to the search keywords and character strings in which characters included in the search keywords only appear here and there have the same degree of similarity. Consequently, the problem exists that the search results have low accuracy in terms of finding documents that the user desires.
In consideration of the foregoing, it is an objective of the present invention to provide a search device, search method and recording medium capable of executing ambiguous searches with high accuracy.